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typedef int QDataType;struct QueueNode {    struct QueueNode* next;    QDataType data;};

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struct Queue {    struct QueueNode* head;    struct QueueNode* tail;};

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void QueueInit(struct Queue* pq) {    assert(pq);    pq->head = NULL;    pq->tail = NULL;}

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void QueueDestroy(struct Queue* pq) {    assert(pq);    struct QueueNode* cur = pq->head;    while (cur) {        struct QueueNode* next = cur->next;        free(cur);        cur = next;    }    pq->head = pq->tail = NULL;}

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void QueuePush(struct Queue* pq, QDataType x) {    assert(pq);    struct QueueNode* newnode = (struct QueueNode*)malloc(sizeof(struct QueueNode));    if (newnode == NULL) {        printf("????!\n");        exit(-1);    }    newnode->data = x;    newnode->next = NULL;    if (pq->tail == NULL) {        pq->head = pq->tail = newnode;    } else {        pq->tail->next = newnode;        pq->tail = newnode;    }}

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void QueuePop(struct Queue* pq) {    assert(pq);    assert(!QueueEmpty(pq));    if (pq->head->next == NULL) {        free(pq->head);        pq->head = pq->tail = NULL;    } else {        struct QueueNode* next = pq->head->next;        free(pq->head);        pq->head = next;    }}

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QDataType QueueFront(struct Queue* pq) {    assert(pq);    assert(!QueueEmpty(pq));    return pq->head->data;}

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QDataType QueueBack(struct Queue* pq) {    assert(pq);    assert(!QueueEmpty(pq));    return pq->tail->data;}

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bool QueueEmpty(struct Queue* pq) {    assert(pq);    return pq->head == NULL;}

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int QueueSize(struct Queue* pq) {    int size = 0;    assert(pq);    struct QueueNode* cur = pq->head;    while (cur) {        size++;        cur = cur->next;    }    return size;}